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C /98o ov 7 <br />%2 -/ZU <br />Kaldenbach, Tom /?eVo"scs <br />From: Welt, Kathy [KWelt@archcoal.com] <br />Sent: Wednesday, April 07, 2010 4:16 PM <br />To: Kaldenbach, Tom <br />Cc: Nolte, Doug; Nyikos, Chris; Paul T. Swenson <br />Subject: RE: West Elk Mine (C-1980-007), TRA20 <br />Tom, <br />Barr Engineering has provided the following responses to your April 5th comment letter on TR-120. <br />CDRMS Comment 8(a): Please provide revised SEDCAD runs (or other similar analyses) for <br />Appendix F that evaluate the east and west sediment ditches as pipes (rather than ditches), <br />and revise associated text references. <br />Response: The SEDCAD runs in Appendix F have been revised to evaluate the east and <br />west sediment ditches as pipes and the SEDCAD text no longer refers to ditches. <br />2. CDRMS Comment 8(b): To ensure compliance with Rule 4.09.2(7), please revise the design <br />of the east and west sediment pipes so they are off the fill. Also, please add to Section 3.2 the <br />diameter of the sediment pipes, the dimensions of the manholes, and identify the construction <br />materials of these structures. <br />Response: The design of the east and west sediments pipes, as shown in revised Figures <br />C-13 and C-15, has been altered so that the pipes are off the fill. <br />3. CDRMS Comment 8(c): Please add to Appendix F a SEDCAD run (or other similar analyses) <br />for the east and west clear water diversion ditches that includes runoff from the surface of the <br />reclaimed RPE East after final reclamation (see following comment 11). <br />Response: MCC intends that the sediment pipes stay in place and continue to route refuse <br />pile surface runoff after final reclamation is completed. The reasons for leaving these <br />structures in place are as follows: <br />Since the sediment pipes will be installed below the ground surface to provide <br />stability to the pipeline, removing the pipes would require excavating cover soils over <br />the pipe, as well as reestablishing equipment access to the entire perimeter. <br />Leaving the pipes in places will avoid significant redisturbance to the fully reclaimed <br />and revegetated project area. <br />As the project area will have been fully reclaimed, the haul roads used to access the <br />RPE East would have also been removed, prohibiting the access necessary for <br />construction equipment to remove the piping infrastructure.